1. Field of the Invention
The present invention relates to the field of thin film deposition technologies for allowing real time in-situ measurements of deposited thin films.
2. Description of the Related Art
Real time in-situ measurements of deposited thin films formed on the surfaces of a substrate in a thin film deposition furnace are quite important for depositing the thin film with high accuracy.
An optical thin film measuring apparatus taking advantage of laser interferometry has been known in the art as the thin film measuring apparatus as described above.
This optical thin film measuring apparatus is particularly applied for measuring a transparent thin film such as a dielectric material. In this optical thin film measuring apparatus, a laser beam is irradiated on the surface of a thin film deposition substrate disposed in a thin film forming furnace, and the intensity of the beam reflected from the surface is sensed using a photo-cell. The intensity of the reflected light sensed with the photo-cell exhibits a periodic characteristic due to interference between the reflected light from the surface of the substrate and the reflected light from the surface of the thin film, and the thickness of the thin film is measured by the number of interference cycles.
However, the conventional optical thin film measuring apparatus involves a measuring limit ascribed to the wavelength of the light used, and a measuring accuracy exceeding the critical accuracy cannot be expected.
Required levels in the industrial fields for the production of the thin film have became quite high in recent years, often claiming a quite high level accuracy of several angstroms for the thickness of the thin film. Accordingly, a thin film measuring apparatus that can replace the optical thin film measuring apparatus has been desired.